ERBB2 and breast cancer: Of 545 patients, 302 (55.4%) were below 50 years of age, 315 (57.8%) were premenopausal, and most had T2 (76.1%) tumor and N1 (45.5%) lymph node status; 334 (61.3%) patients had HR-positive breast cancer and 108 (19.8%) patients had HER2 IHC 2+ disease with confirmed amplification by FISH.